For the generation of a possibly fine spectrum of droplets, spray nozzles are used with an output or a mixing chamber and at least two through bores leading to the output or mixing chamber, which are respectively connected with a fluid line, in particular the so-called two-component nozzles. A disadvantage of these two-component nozzles is the proneness to solid sediment, in particular, also in the supply-air bores. Safe operation of two-component nozzles, in many cases, requires frequent removal of the nozzle lances on which spray nozzles are arranged. Only in this manner are nozzles accessible for cleaning according to the state of the art.
In process engineering, in particular, in the case of flue-gas cleaning nozzles are frequently used, which allow very fine atomisation of liquid. Besides high-pressure single-component nozzles, also two-component nozzles are finding increasing application. With such nozzles, also, the liquid is atomised under the influence of a pressurised gas, e.g., compressed air or steam under moderate pressure. With such known two-component nozzles, equipment failures occur relatively frequently through sedimentation in the through bores towards the output or the mixing chamber. Narrow parts of a liquid inlet into the mixing chamber are normally affected, but also, in particular, most radially located bores for introducing compressed air into the mixing chamber are also affected. This compels frequent removal of nozzle lances and cleaning of the nozzles. Since the systems in which the nozzles are fitted, in particular, for flue-gas cleaning cannot be generally shut down for this purpose, these requirements limit the application of the two-component nozzles substantially, since a negative pressure must normally prevail in the system at the nozzle insertion flange, so that hazardous gases cannot exit at the flange briefly opened to remove the nozzle lances. Furthermore, the maintenance work necessitates a significant period. The function of the system can be impaired by the removal of a nozzle lance to facilitate maintenance work.
The object of the invention should broadly inhibit dirt-collection on the spray nozzles, so that long maintenance-free operation intervals of such spray nozzles and spray devices can be achieved.
According to the invention, for this purpose, a spray nozzle with an output or a mixing chamber and at least two through bores leading to the output or to the mixing chamber are provided, wherein the through bores are respectively connected with a fluid line in which at least one of the through bores is formed in a self-cleaning manner and/or devices are provided for cleaning at least one of the through bores.
By means of the spray nozzle according to the invention, the occurrence of sediment on the through bores is prevented in that said bores are made in a self-cleaning manner or additional devices are provided for cleaning at least one of the through bores. The self-cleaning process thereby occurs during a spraying operation and the cleaning devices remove any sediment inside the through bores during the spraying or a cleaning operation.
In a further embodiment of the invention, at least one of the through bores features a tapering cross-section, on its side oriented away from the output or from the mixing chamber, rounded in such a manner that a fluid flow passes the through bore up to the orifice into the mixing chamber, without flow separation/burbling.
The formation of sediment inside the through bores is prevented in this manner, since shearing stress is generated on the bore walls, by the fluid flow in the direction towards the mixing chamber. The wall shearing stress prevents fluid backflow into the bores, so that the formation of sediments is broadly inhibited.
In a further embodiment of the invention, the through bore is rounded like a nozzle on its side oriented away from the mixing chamber.
In this manner, it is reliably prevented that the fluid flow separates from the wall of the through bore.
In a further embodiment of the invention, at least one of the fluid lines is formed as a liquid supply line to the mixing chamber and in an area of at least one through bore, a movable tappet is provided for cleaning inside the liquid inlet bore.
Such a tappet can reliably ensure that any sediment is again dissolved and removed. The tappet, for example, can be actuated by magnetostrictive or hydraulic means.
In a further embodiment of the invention the tappet is located upstream of the liquid inlet bore and formed conical or truncated-cone-like in shape on its end oriented towards the liquid inlet bore.
A reliable cleaning effect is attained by means of such a formation.
In a further embodiment of the invention, the tappet is located in the supply line towards the liquid inlet bore with its longitudinal direction parallel to the flow direction and formed tapering on both ends.
In this manner, the tappet can be shaped for convenient flow and the resistance to flow, caused by the tappet in the liquid supply line, can be kept low.
The conical or truncated-cone-shaped end of the tappet is advantageously matched to an inlet area of the liquid inlet bore, said inlet area tapering in the flow direction.
In a further embodiment of the invention, one of the fluid lines is formed as a liquid supply line and means are provided to apply pressure surges to the liquid in the liquid supply line.
The pressure surges can be used for cleaning the through bores. It is advantageous in the process that no mechanical devices must be introduced into the through bore and that the pressure surges can be applied during the spraying operation.
Advantageously, pressure surges having frequencies in the ultrasonic range are applied. In this manner, possible sediment can be comminuted and carried away via the mixing chamber of the nozzle. In a certain sense, the cleaning effect that occurs is comparable with the ultrasonic comminution of kidney stones.
In a further embodiment of the invention one of the fluid lines is formed as a pressurised gas supply line to a mixing chamber and upstream of the at least one through bore formed as a pressurised gas inlet bore, means are provided for introducing abrasive dust into the pressurised gas supply line.
Sediment can be removed by erosive means of abrasive dust particles. The hardness of fine abrasive dust should be substantially lower than the hardness of the nozzle material.
In a further embodiment of the invention one of the fluid lines is formed as a pressurised gas supply line to a mixing chamber and upstream of the at least one through bore is formed like a pressurised gas inlet bore where means are provided for introducing cleaning liquid into the pressurised gas supply line.
Such a cleaning liquid can for example be demineralised water and the pressurised gas is applied with an aerosol of the cleaning liquid. It can be helpful in the process to apply the cleaning liquid with chemicals to assist the sediment-dissolving process inside the through bores. It is not necessary to dope the atomising air perpetually with cleaning liquid, but rather, in many cases, also intermittent application can be sufficient. If necessary, a separate atomising chamber can be provided to atomise the cleaning liquid into tiny droplets prior to introduction into the pressurised gas supply line.
In a further embodiment of the invention, one of the fluid lines is formed as a pressurised gas supply line to a mixing chamber and upstream of at least one through bore is formed as a pressurised gas inlet where means are provided for introducing foamed or foam-like particles into the pressurised gas supply line, which can be pressed through the pressure inlet bore by means of the pressure of said gas.
By means of such foamed or foam-like particles, for example in spherical shape, sediment or clogging pieces can be removed or prevented. Typically, several pressurised gas inlet bores are provided and the cleaning particles are pressed through all the through bores in accordance with the stochastic natural law.
In a further embodiment of the invention one of the fluid lines is formed as a pressurised gas supply line to a mixing chamber and upstream of the at least one through bore that is formed as a pressurised gas inlet bore, means are provided for introducing steam into the pressurised gas supply line.
The introduction of steam can already generate sufficient cleaning effect.
In a further embodiment of the invention one of the fluid lines is formed as a liquid supply line and the through bore formed as a liquid inlet bore features a constriction, wherein a ratio of length to diameter of the constriction is greater than 1.0, in particular greater than 1.5. Sediments in the liquid inlet bore can lead to the liquid that flows into the mixing chamber to be deflected laterally. Due to the corresponding dimension of the constriction, the liquid jet itself is then broadly fed in to the mixing chamber, centrally and symmetrically when sediment has collected in the form of scales in front of the constriction.
In a further embodiment of the invention one of the fluid lines is formed as a liquid supply line to a mixing chamber and one of the fluid lines as a pressurised gas supply line to the mixing chamber, wherein the pressurised gas supply line surrounds the mixing chamber, at least section wise, in the form of a ring and several through bores that are formed as pressurised gas inlet bores relative to a middle axis of the spray nozzle are arranged radially towards the mixing chamber.
Such a formation allows generation of very fine droplets, and together with the measures according to the invention, dirt-formation is extensively prevented on such a two-component nozzle.
The problem based on the invention is also solved by means of a method for operating a spray nozzle according to the invention, in which the step of introducing a cleaning fluid or cleaning particles in a fluid line that is formed as a pressurised gas supply line upstream of at least one through bore that is formed as a pressurised gas inlet bore is provided into the mixing chamber.
By introducing a cleaning fluid or cleaning particles, any sediment accumulated inside the through bores of the spray nozzle can be removed reliably and for example flushed away together with the spray jet. For example, steam, chemically active cleaning liquid or fine abrasive dust can be introduced upstream of the at least one pressurised gas inlet bore. Alternatively or additionally, it is also possible to introduce foam or foam-like cleaning particles upstream of the at least one pressurised gas inlet bore, which are then pressed through the pressurised gas inlet bores into the mixing chamber, under the effect of the pressurised gas.
In a further embodiment of the invention, it is provided that pressure surges are modulated on the liquid to be atomised in the fluid line formed upstream as the liquid supply line on the at least one through bore formed into the mixing chamber.
By means of such pressure surges, impurity or sediment in the through bores can be dissolved likewise in a reliable manner. For example, pressure surges can be modulated with frequencies in the ultrasonic range, in order to comminute sediment in the through bores or on other parts of the nozzle.
The problem according to the invention is also solved by means of a spray device with a spray nozzle according to the invention in which means are provided in order to cause fluid flow from the mixing or output chamber into the fluid line during a cleaning operation, in at least one of the fluid lines and the associated through bore.
A cleaning effect can be achieved through a fluid flow from the mixing or output chamber into the fluid line. The fluid to be sprayed for instance can be a liquid or a liquid-solid suspension. The spray device according to the invention can be used with two-component nozzles or also with the so-called single-component back-flow nozzles, in which a part of the fluid flowing into the output chamber does not exit the nozzle but rather flows back into a return line. In an extreme case, in the case of single-component back-flow nozzles, the return-flow volume is equal to the supply volume, so that no fluid is injected into gas space. This effect can be used for a cleaning operation. In particular, in two-component nozzles, a reverse flow direction is set in a cleaning operation between a mixing chamber and a liquid supply line or rather, if applicable, a filter is connected downstream in contrast to the spraying operation. By reversing a flow direction in a cleaning operation in contrast to the spraying operation, sediment or clogging pieces can generally be removed in a reliable manner.
In a further embodiment of the invention, the fluid lines feature a pressurised gas supply line to the mixing chamber and a liquid supply line to the mixing chamber and the means for reversing the flow direction in the cleaning operation causes an outward fluid flow from the mixing chamber through the liquid inlet bore and an inward flow into the liquid supply line.
In this manner, the liquid inlet bore can be cleaned reliably in a cleaning operation.
In a further embodiment of the invention, a fluid line formed as a liquid supply line features at least a shut-off valve and at least a cleaning valve located downstream of the shut-off valve in the liquid supply direction.
After opening the cleaning valve, the fluid flowing relative to the spraying operation can be let out through the cleaning valve in the reverse direction, so that possible dirt or sediment can be carried away from the spray device.
In a further embodiment of the invention a negative pressure source is provided, which can be connected by means of the cleaning valve with the liquid supply line.
In this manner, the back-flow amount into the liquid supply line can be increased, but by applying a correspondingly high negative pressure, for example, it can also be prevented that liquid or pressurised gas exits from the output orifice of the nozzle into the process surrounding during the cleaning operation.
In a further embodiment of the invention a sludge-collection tank is provided, which can be connected with the liquid supply line by means of the cleaning valve.
Sediments can be collected in a sludge-collection tank.
In a further embodiment of the invention a filter device is provided, which is serially switched into the liquid supply line and a filter chamber is provided respectively on the upstream and downstream side of a filter insert, wherein both filter chambers may be connected by means of a cleaning valve respectively with a sludge-collecting tank.
In this manner a filter device can also be cleaned in a cleaning operation with reverse flow. The dissolved sediments during a cleaning operation are collected in the filter chamber located downstream in a spraying operation. In normal spraying operation the impurities of the supplied liquid to be sprayed will collect in the filter chamber located upstream. In a cleaning operation, both filter chambers can be emptied and connected, for example, with a sludge-collection tank via the sludge-collection line.
In a further embodiment of the invention one of the fluid lines is formed as a pressurised gas supply line and a means for introducing a cleaning liquid is provided in the pressurised gas supply line.
In a further embodiment of the invention a collection tank is provided for the cleaning liquid and a means for conveying the cleaning liquid from the collection tank is provided in the pressurised gas supply line.
In this manner, the cleaning liquid can be circulated in the spray device according to the invention, for example, for so long until its cleaning effect is exhausted. In this manner, a very economical operation of the spray device according to the invention is possible.
In a further embodiment of the invention means are provided in the liquid supply line, for mixing the cleaning liquid from the collection tank during the spraying operation.
In this manner, effluent-free operation of the spray device according to the invention can be achieved, since the cleaning liquid used for the cleaning operation is first collected in a collection tank and then during the spraying operation metered again into the liquid to be sprayed. The mixing process can thereby occur, in that the cleaning liquid in the spraying operation is drained from the spray nozzle after being diluted up to ineffectiveness. An already existing sludge-collection tank can be used as a collection tank.
The problem on which the invention is based is also solved by a method of operating a spray device according to the invention, in which the step of reversing the fluid-flow direction in a cleaning operation in contrast to a spraying operation is provided in at least one area of the orifice of one of the fluid lines into the mixing or output chamber.
In this manner, impurities that have collected in front of the through bores during the spraying operation are flushed away in the reverse cleaning operation direction.
In a further embodiment of the invention, a fluid line of the spray nozzle is formed as a liquid supply line leading to the mixing chamber and another fluid line as a pressurised gas supply line leading to the mixing chamber and the following steps are provided:
In a cleaning operation, a liquid supply is switched off by means of a shut-off valve in the liquid supply line, and a cleaning valve is opened in the liquid supply direction downstream of the shut-off valve, a cleaning fluid flow is introduced via the gas supply line, and then the mixing chamber in the liquid supply line, then to the cleaning valve.
Through this measure, the cleaning fluid-flow crosses the mixing chamber against the spraying operation in the reverse direction, so that clogging pieces or impurities can be removed from through bores. The cleaning fluid can thereby be pressurised gas that is used during the spraying operation.
In a further embodiment of the invention a negative pressure can be applied at the cleaning valve during the cleaning operation.
In this manner, on the one hand, the change of direction of flow can be supported during the cleaning operation, and it can also be prevented during the cleaning operation that the cleaning fluid exits from the spray nozzle.
In a further embodiment of the invention the cleaning fluid is a mixture of pressurised gas and cleaning liquid. Alternatively, the cleaning fluid can exclusively consist of cleaning liquid. Moreover, during the cleaning operation, the surrounding gas can be sucked through a nozzle output orifice, so that the cleaning fluid contains the surrounding gas. For example, flue gas can be sucked in, if it may be assumed that the properties of the flue gas from the process surrounding does not impair the dissolution of sediment.
In a further embodiment of the invention it is provided that the cleaning fluid circulates from the cleaning valve to the pressurised gas line through the mixing chamber and the liquid supply line and back to the cleaning valve.
In this manner the cleaning fluid can be used several times. The cleaning fluid can then be collected in a collection tank during the cleaning operation to attain an effluent-free operation during the spraying operation, and again be admixed from the collection tank in the liquid supply line.
Further features and advantages of the invention result from the following description of preferred embodiments of the invention in combination with the drawings. In so-doing, individual features of differently depicted embodiments can be combined with one another in an arbitrary manner, without departing from the scope of the invention. The drawings show: